1. Field of the Invention
The present invention relates to a conveyance system in a semiconductor manufacturing process and a method for processing semiconductor wafers therein, more particularly, to a method for controlling the conveyance system to shorten a TAT (Turn Around Time) during the semiconductor manufacturing process.
2. Description of the Related Art
In the related art, a semiconductor manufacturing system comprises a wafer storage for temporary storing semiconductor wafers, an automatic conveyer for conveying the semiconductor wafers, a conveyer controller for controlling the automatic conveyer, a process unit for cleaning, drying, and etching the semiconductor wafers, and a computer for administrating and controlling the semiconductor manufacturing system. The semiconductor wafers are conveyed from the wafer storage to the process unit, or from the process unit to the another process unit in response to specific instructions form the computer.
For example, in the case that the semiconductor wafers are conveyed from the process unit A to the process unit B, the computer receives a signal from the process unit A, indicating that a process of the semiconductor wafers has been completed in the process unit A, and then the process unit B which can perform the next process is searched by the computer, and simultaneously, the computer judges whether or not the process unit B is located in the same area of the process unit A or not. In the event that the process unit B is not located in the same area as the process unit A, the computer instructs the conveyer controller to let the semiconductor wafers be conveyed to the wafer storage. In the case that the process units A and B are located in the same area, the computer judges whether or not the semiconductor wafers can be conveyed to the process unit B. If not, the computer instructs the conveyer controller to let the semiconductor wafers be conveyed to the wafer storage. If yes, the computer instructs the conveyer controller to let the semiconductor wafers be conveyed to the process unit B.
However, in the semiconductor manufacturing system mentioned above, since the signal indicating the completion of the process is sent to the computer from the process unit after the process is actually completed, the semiconductor wafers being processed can not be conveyed just after completion of the process. As mentioned above, since the automatic conveyer is moved to the process unit in response to the instruction from the computer, it will take a few minutes to reach the process unit. That is, the semiconductor wafers being processed have to wait at the process unit for a few minutes until the automatic conveyer reaches there. Therefore, the waiting time of the semiconductor wafers being processed which is the period from the time of the process completion until the time of the arrival of the automatic conveyer, causes a delay for the production TAT. Furthermore, this delay causes another delay in a later process. Further, during the conveyance of the semiconductor wafers from a wafer process unit to the assemble process unit, the semiconductor wafers could be left out of the search list of the computer by the delay even if the semiconductor wafers to be processed in the assemble process should be listed for the computer search. Furthermore, the assemble process unit is halted for awaiting the arrival of the semiconductor wafers where the semiconductor wafers under the conveyance is the only object to be processed.